Robot for minimally invasive neurosurgery

ABSTRACT

A robotic device for performing intracranial procedures, comprising a baseplate for mounting on the subject&#39;s skull and a rotatable base element rotating on the baseplate. The rotatable base element has a central opening through which a cannulated needle can protrude such that it can rotate around an axis perpendicular to the baseplate. This cannulated needle is robotically controlled to provide motion into and out of the subject&#39;s skull. A flexible needle is disposed coaxially within the cannulated needle, and it is controlled to move into and out of a non-axial aperture in the distal part of the cannulated needle. Coordinated control of the insertion motion of the cannulated and flexible needles, and rotation of the combined cannulated/flexible needle assembly enables access to be obtained to a volume of a region of the brain having lateral dimensions substantially larger than the width of the cannulated needle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/941,607, filed Jul. 15, 2013, which is a continuation-in part of PCTInternational Application No. PCT/IL2012/000022, which has aninternational filing date of Jan. 15, 2012, and which claims the benefitof priority from U.S. Provisional Patent Application No. 61/457,147,filed on Jan. 14, 2011, the disclosures of which are incorporated hereinby reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to the field of robotic systems for use inminimally invasive surgical and diagnostic procedures, especially foruse in performing cranial neurosurgery.

BACKGROUND OF THE INVENTION

As of today, brain surgeries remain complex and risky. Conventional openskull surgery is traumatic, may have debilitating side effects to thepatient and generally requires long recovery time. The time taken toperform the surgery may be tedious and decreases the efficiency of themedical staff. The complexity of the operations often preventsrepeatability if required. The operation itself may cause a brain-shift,and for operations such as tumor resection, the original position of thetumor may be dislocated so that pre-operative planning may no longer beaccurate intraoperatively.

There therefore exists a need for a minimally-invasive and automatedprocedure, which overcomes at least some of the disadvantages of priorart procedures, in particular, in avoiding major trauma to the brain inareas other than that to be operated on, and in doing so, avoidingsignificant brain-shift, such that the pre-operative planning is stillvalid intra-operatively.

The disclosures of each of the publications mentioned in thisspecification, are hereby incorporated by reference, each in itsentirety.

SUMMARY OF THE INVENTION

The present disclosure describes new exemplary automated robot-basedplatforms for minimally-invasive neurosurgical use, including proceduressuch as resection of brain tumors or the extraction of multiple biopsysamples from large volumes of the brain, or others. Unlike otherexisting robotic approaches that mimic the surgeon's hand motion, andwhich therefore generally require substantive access to the operationregion, the presently described technology uses the unique capabilitiesof robotic systems for minimally invasive access to regions of the brainwith minimal collateral tissue damage, on the basis of predeterminedmotion of the robotic actuator holding the surgical tool, which isaccurately positioned and moved by the robotic control. The region ofthe brain to be treated is first mapped using an imaging modality suchas CT, MRI or Ultrasound. Based on these images, the surgeon decides onthe best path to reach the tumor, if that is the target of theprocedure, with minimal trauma to surrounding brain tissue. Minimizationof such trauma is important in reducing brain shift, thereby maintainingthe spatial accuracy of the preoperative images.

Some prior art robotic systems for neurosurgery, such as the NeuroMatesupplied by Renishaw plc of Wotton-under-Edge, Gloucestershire, U.K.,access the brain along one trajectory line and can make a procedure suchas a biopsy, or a DBS only along that line. The present inventionenables access to a larger volume through a single entrance passage. Asa result, less brain tissue is damaged during the access process. Asmall key-hole incision is made in the skull, and a narrow path istraced by the robotic tool to reach the desired location. The robotadvantageously consists of a rigid cannulated outer needle with adistally positioned laterally directed hole. A flexible needle isadvanced through the bore of the cannulated needle, and delivered to thediseased area through the distal hole. This hole can be angled at anyorientation relative to the rigid cannulated outer needle, but optimumaccess for the flexible needle is achieved if the hole is aligned atright angles to the axis of the outer cannula. The motion of the twoneedles are computer controlled such that every point in the vicinity ofthe distal end of the needle can be reached by controlling the insertiondepth and the orientation of the rigid needle, and the relativeinsertion depth of the flexible needle. Using such an arrangement aninsertion path width of less than 5 mm is possible. When the desiredlocation is reached, the surgical tool at the end of the flexible needlecan be actuated to treat the accessible volume of the tumor. Theflexible needle is constructed such that it, or another surgical tool orprobe inserted down it, more can perform physical cutting operations, orcan deliver an electric current, ablative or phototherapeutic heat orlight, or ultrasound energy to treat, for instance, a tumor, or canincorporate a miniature camera to image the region of interest. For drugdelivery the internal flexible needle can be cannulated. For biopsiesthe needle may be constructed to extract tissue samples. By this means,multiple samples over a large volume to be inspected, can be taken usingonly one small incision. Access to regions of the brain beyond theoperational access of the flexible needle end in a single extension canbe reached by withdrawing the flexible needle to within the rigidcannulated needle, and then withdrawing the rigid cannulated needlesomewhat, or inserting it further, in order to reposition it to provideaccess by the inner flexible needle to the new region to be accessed,whether into a deeper or a less deep region of the brain, and atwhatever azimuthal angle is needed relative to the first treatmentperformed.

The needle motion can be controlled in two modes:

1. Based on pre-operative planning, whereby the shape and position ofthe diseased area is known from preoperative images, and hence themotion needed to reach specific points within the diseased area isknown. This mode will require a registration procedure to be performed,generally using markers having known positions and visible in thepreoperative images, in order to relate the robotic co-ordinate systemto the co-ordinate system of the images. Alternatively, registration canbe achieved by surface matching techniques, whereby an intra-operativescan of the subject's head, including at least some anatomic featuressuch as the subject's facial features, and some known features of themounted robot, is compared with a preoperative scan of the subject'shead. Matching of the anatomical features then enables the position ofthe robot to be determined relative to the preoperative images.2. Real time control using an external or internal imaging system, suchas MRI, CT, ultrasound, or needle mounted sensors. The latter option mayuse optical, electrical or ultrasound sensors, mounted on either or boththe flexible needle and the external rigid needle. Such needle mountedsensors can then be used to detect not only the position of the needletip, but also to provide data regarding the physiological state andcondition of the surrounding tissue.

As an alternative to use of the base element fixed directly to theskull, it is possible to use any of the conventional mounting hardwaresuch as a stereotactic frame in order to attach the needle assembly in apredetermined position to the patient's skull. In such a case, prior artmethods can be used to determine the direction of penetration of thetreatment needle. In such prior art methods, the region to be treated isdefined on preoperative images, which include the mounting hardware usedto support the needle insertion device, and the position of the devicerelative to the mounting hardware is known, such that the device isregistered to the preoperative images. The surgeon then defines theorientation angles and depth of penetration of the needle, using thealignment facilities provided on the mounting hardware. Using prior artmethods of a single needle inserted straight into the patient's brain,there may be situations where access to the target point is problematicbecause of sensitive or damage prone regions of the brain in the directlinear access path. Use of the present device enables access to beachieved along a singly articulated path without encountering thesensitive or damage-prone regions of the brain.

Additionally, if adjustable mounting hardware is used, it is possible toaccess in two dimensions, locations which would otherwise be problematicto reach by a direct linear path. The specific target area is reached byfirst aligning the device using the mounting frame adjustments, and thena controlled sequential combination of (i) the depth of entry of thecannulated needle and then (ii) the extension of the flexible needle, toreach the target area.

The surgeon can at any time, take active control of the robot and changethe operation plan if necessary.

The small access path minimizes brain shift during the surgery andimproves operation accuracy and reduces morbidity. This technologyallows the robot to reach more areas in the brain from a single cranialincision than previously possible, and opens new horizons in treatingbrain tumors.

In US Patent Application Publication No. 2009/0048610 to G. Tolkowsky etal., for “Medical Probe Introducer” there is described a hand operatedmechanical system for inserting a probe into the subject's cranialtissue, in which the off axis target of the probe or the treatment isreached, either by a use of a straight needle with an angled treatmentoutlet, or by use of a needle constructed of a shape memory alloy, whichbends on exiting its outer cannula in order for the tip to reach thetreatment area. However, the need for such a shape memory needle totraverse a curved path on exiting its outer cannula introduces levels ofaccuracy which may be problematic for such treatments, since unlike astraight needle, it is not clear that the tip will proceed in an arcuatepath to its intended target. Additionally, a curved path may aggravatethe problem of brain-shift. Furthermore, the system described therein ismicrometer based, such that it is slow, and depends on the settingsadjusted by the surgeon for accuracy of insertion.

In US Patent Application Publication No. US 2004/0059260 to C. L.Truwit, for “Method and Device for Deflecting a Probe”, there isdescribed a method and device for inserting a flexible needle down acannula having an off-axis exit aperture, such that as it exits from thecannula, the needle can access a region off-axis from the region towhich the straight cannula can reach.

However, in neither of these publications is reference made to thequestion of the mechanical properties of the materials of the flexibleneedle, and the required shape of a flexible needle in order for it toachieve its aim. There are two conflicting requirements for aneurosurgical device of the type described in this disclosure. In thefirst place, the outer diameter of the external cannular needle shouldbe as small as possible in order to reduce trauma to healthy braintissue to a minimum. Ideally, as previously mentioned, an outer diameteras small as 4 mm is desirable, which means that its inner diameter willbe of the order of 3 mm. However, the outer diameter of a usefulflexible needle incorporating a surgical tool or having a probe orsensor threaded through it, for performing the required operative ortherapeutic procedure, should be of the order of no less than 3 mm.Thus, the inner flexible needle has the severe requirement of having anouter diameter of the order of 3 mm, and yet having the ability to makea 90° bend with a radius of curvature of no more than 3 mm, since theexit aperture path should be contained within the outer cannula externaldiameter limits, as otherwise, it would interfere with the smoothinitial insertion of the outer cannula into the brain tissue.Furthermore, after achieving this bend, the flexible needle should besufficiently strong to be capable of penetrating brain tissue, towithstand lateral forces due to anisotropic nature of the brain tissue,to deploy in a straight line to reach the desired target region with theaccuracy required, and to support any axial force which may be requiredfor it to perform its surgical or therapeutic function, or which may beoperative on it while moving through the brain tissue. These conflictingrequirements mandate novel and inventive configurations of the systemand of the flexible needle.

In this disclosure four different solutions are proposed in order toachieve these objectives, as follows:

(a) Use of thin-wall tube structural buckling, where a change in shapeof the flexible needle occurs while negotiating the turn, restoring tooriginal shape as it exits the turn. Analysis of such tube bucklingunder pure bending and optimum shapes of the flexible needle for thepurposes of this application are described in the detailed descriptionsection hereinbelow.(b) A hollow chain of magnetic beads, separated from each other at thebend and rejoined upon exit. A quasi-static analysis of magnetic beadchain and some examples are described in the detailed descriptionsection hereinbelow.(c) Use of an annular balloon structure, which is sufficientlypressurized and yet sufficiently flexible that after negotiation of thecurve, it maintains its original resistance to axial and lateral forces.(d) Use of tensegrity structures. A tensegrity structure can be locallyun-deployed and weakened in order to negotiate the turn, yet becomefully deployed at its full structural strength upon exit. A fullerdescription of this solution is detailed description sectionhereinbelow.

There is thus provided in accordance with an exemplary implementation ofthe devices described in this disclosure, a robotic device forperforming an intracranial procedure at a target region of a subject'sbrain, comprising:

(i) a baseplate adapted for mounting on the skull of a subject,

(ii) a rotatable element disposed on the baseplate, and having anopening in its central region,

(iii) a cannula mounted on the rotatable element coaxially with theopening, and which rotates with rotation of the rotatable element, thecannula being robotically controlled to provide motion into and out ofthe skull of the subject, and

(iv) a flexible needle disposed in the cannula, the flexible needlebeing controlled to provide motion into and out of a non-axial aperturein the distal part of the cannula, and having a structure adapted toenable it to exit the non-axial aperture and to continue the motion outof the aperture to the target region without losing its mechanicalproperties,

wherein coordinated control of the insertion motion of the cannula andthe flexible needle and rotation of the rotatable element enables accessto be obtained by the flexible needle to the target region of the brain.

In such a robotic device, the non-axial aperture may comprise a curvedsection of the cannula, exiting the cannula at right angles to the axisof the cannula, and having a radius of curvature no more than 25% largerthan the external diameter of the cannula.

The flexible needle may comprise a thin-wall tube having an oval shapewith its shorter dimension being in the same plane as that including theaxis of the cannula and the non-axial aperture, or a thin-wall tubehaving a toroidal shape with its shorter dimension being in the sameplane as that including the axis of the cannula and the non-axialaperture.

In alternative implementations, the flexible needle may comprise ahollow chain of magnetized beads, which should be magnetized in adirection such that they are attracted in a self-centering stack.Alternatively, the flexible needle may comprise an annular inflatedballoon, or an elongated tensegrity structure. In any of these roboticdevices, the flexible needle advantageously may have an outer diameterof less than 4 mm.

Additional implementations can include such a robotic device in whichthe device is adapted to provide access to the target region of thebrain with any collateral trauma to non-accessed parts of the brainbeing approximately confined to a region having the width of thecannula.

Furthermore, the device could be such that coordinated control of theinsertion motion of the cannula and flexible needles and rotation of therotatable element enables access to be obtained by the flexible needleto the target region of the brain along an articulated path selected toavoid damage-prone regions of the brain. The flexible needle maycomprise a cutting tool, such that resection of a brain tumor can beperformed with collateral trauma to those parts of the brain not beingtreated being approximately confined to a region having the width of thefirst cannulated needle.

Yet other implementations may involve a robotic device of the typedescribed hereinabove, wherein the flexible needle is adapted to beconnected to an energy delivery system, such that ablation or optical orelectro-treatment of a brain tumor can be performed with collateraltrauma to those parts of the brain not being treated being approximatelyconfined to a region having the width of the first cannulated needle.Such a flexible needle may comprise an optical fiber for delivery of theenergy.

Additional implementations can include a robotic device in which theflexible needle may comprise a biopsy tool, such that biopsy samples maybe obtained from regions of the brain at different positions laterallydisplaced from each other by distances substantially larger than thewidth of the first cannulated needle, with collateral trauma to thoseparts of the brain not being accessed being approximately confined to aregion having the width of the first cannulated needle. Alternatively,the flexible needle may comprise a drug delivery passage.

Further example implementations may involve a robotic device furthercomprising a set of preoperatively inserted markers for relating theposition of the robotic device to the skull of a subject, such that theco-ordinate system of the robotic device can be registered to apreoperative image of the skull of the subject. Alternatively, therobotic device may further comprise at least one position sensordisposed in the distal region of the flexible needle, such that the realtime position of the flexible needle tip can be monitoredintraoperatively, or in the distal region of the cannula, such that thereal time position of the tip of the cannula can be monitoredintraoperatively.

Yet other implementations perform a method of performing intracranialprocedures, comprising:

(i) providing a baseplate and mounting it on the skull of a subject, thebaseplate having disposed on it a rotatable element with an opening inits central region,

(ii) mounting on the rotatable element, coaxially with the opening, anassembly comprising:

(a) a cannula which rotates with rotation of the rotatable element, thecannula being robotically controlled to provide motion into and out ofthe skull of the subject, and

(b) a flexible needle disposed in the cannula, the flexible needle beingcontrolled to provide motion into and out of a non-axial aperture in thedistal part of the cannula, and

(iii) coordinating the rotation of the rotatable element and thesequential insertion of the cannula and the flexible needle to enableaccess to be obtained by the flexible needle to a target region of thebrain where the procedure is to be performed.

Alternative implementations involve a method of performing neurosurgicalprocedures at a target region of the brain, comprising:

(i) attaching in a predetermined orientation and position on the skullof a subject, a base element,

(ii) mounting on the base element, an assembly comprising:

(a) a cannula, the cannula having a non-axial aperture in its distalpart, and a motion controller to provide motion into and out of theskull of the subject, and

(b) a flexible needle disposed in the cannula, the flexible needlehaving a motion controller to provide motion into and out of thenon-axial aperture in the distal part of the cannula,

(iii) selecting on a preoperative image of the brain, a singlyarticulated path avoiding damage-prone regions of the brain, and

(iv) controlling the sequential insertion motion of the cannula and theflexible needle to enable access to be obtained by the flexible needleto the target region of the brain along the singly articulated path.

In either of these methods, the flexible needle may be a thin-wall tubehaving an oval or a toroidal shape, or any of a hollow chain ofmagnetized beads, an annular inflated balloon, or an elongatedtensegrity structure.

It is to be understood that the term flexible needle, as used and asclaimed in the present application is intended to apply to the elementinserted through the bore of the external rigid cannula, whether thatelement is a full needle, such as for delivering a biopsy harvestingtool, or a sensor or an electrode, or the like, or whether that needleis hollow, such as for drug delivery, or for extracting a fluid sample,or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be understood and appreciated more fully from thefollowing detailed description, taken in conjunction with the drawingsin which:

FIGS. 1A and 1B illustrate schematically an exemplary implementation ofa robotically controlled neurosurgical apparatus using a doublecannulated needle assembly, as described in this disclosure;

FIG. 2 illustrates schematically how the complete double needle assemblyof FIG. 1A can be advanced through the holes in the base sections of thedevice, using a motor-encoder assembly;

FIG. 3 illustrates schematically how the internal flexible needle of theassembly of FIG. 2 can be advanced outside of the external rigid needle,so that its tip can reach the regions of the brain which it is desiredto treat;

FIGS. 4A and 4B illustrate alternative methods to that of FIG. 3, ofenabling the tip of the internal needle to reach any part of the regionto be treated;

FIGS. 5A and 5B illustrate schematically the cross section of two typesof oval shaped needles, according to an implementation of flexibleneedles for use in the systems described in FIGS. 1 to 4B;

FIG. 6 illustrates schematically another flexible needle implementationconstructed as a passive magnetic bead chain;

FIG. 7 illustrates a further implementation of the flexible needles foruse in the system of the present disclosure, in the form of aninflatable annular shaped balloon;

FIG. 8 illustrates a flexible needle construction, utilizing atensegrity structure to provide the structural strength combined withthe required flexibility when negotiating the bend at the exit of theouter cannula;

FIG. 9 illustrates schematically a complete practical robotic systembased on the systems shown in the above Figures; and

FIG. 10 illustrates schematically further exemplary implementations ofneedle insertion devices using conventional head clamping devices.

DETAILED DESCRIPTION OF THE INVENTION

Reference is now made to FIGS. 1A and 1B, which illustrate schematicallyan exemplary implementation of a robotically controlled neurosurgicalapparatus according to the novel designs presented in this disclosure. Acentral feature of this neurosurgical robot implementation is acombination of a flexible needle 4 which can be controllably insertedinto an external rigid cannular needle 3. Although the flexible needleis shown in the drawings of this disclosure as a solid needle, it can,as previously mentioned, be either solid or cannulated. The shape of theexternal rigid needle is shown in FIG. 1B. At its distal tip 21, thebore of the external needle is diverted laterally, so that the distalopening is directed sideways from the bore of the needle, at an angle tothe axis of the bore of the needle. In FIGS. 1A and 1B, the exit angleis shown as approximately 45° to the cannula axis, though it is to beunderstood that this angle can be selected to enable ease of passage ofthe flexible needle around the bend of the bore, depending on theflexibility and diameter of the flexible needle 4. The external needleshould advantageously be made of a rigid metal, which should not be aferromagnetic metal if an MRI system is to be used for theintraoperative real-time imaging. The internal needle may be made of aflexible metal such as Nitinol, or, if the stresses to be applied to itare not excessive, of a plastic material, the level of flexibility beingsuch that it can negotiate the bend at the tip of the external needlewhile maintaining its shape after leaving the lateral hole of theexternal needle.

As shown in the exemplary robot of FIG. 1A, the combination of internaland external needles are mounted above an opening in a base section 2,which itself is rotatably mounted on a main base 1. Rotation of the basesection 2 around the main base 1 may be performed by means of a roboticactuation motor 5, which should also include an angular positionencoder, so that the angular orientation of the base section 2 is known.Correct rotation of the base section 2 relative to the opening in thebase section should be ensured, such as by means of a circular slide andguide arrangement, as shown on the top surface of the main base 1. It isalso important that the external cannula 3 and its contents rotates inexact unison with the base, since otherwise, the base encoder would giveincorrect readings for the angular position of the needle assembly. Thiscan be achieved either by ensuring that the rotary friction of theexternal needle with the rotating base is much higher than the expectedfriction force between the brain tissue and the needle after insertion,or by provision of a mechanism to positively fix the angular position ofthe needle assembly to the base, such as a key-way running down thelength of the outer wall of the cannulated needle such that it can sliderelative to the rotating base, but cannot rotate independently thereof.

The insertion of the internal flexible needle within the external needlemay be controlled by means of a robotic motor and encoder 7, as shown inFIG. 1A, or by means of a linear motor (not shown). If a rotary drive isused, access to the flexible needle 4 can be obtained by means of a slotin the external cannula wall. Alternatively, the inner flexible needle 4can be moved from its proximal end section protruding from the externalcannula 3. The linear insertion and extraction motion of the completedouble needle assembly relative to the base plate may be controlled bymeans of another motor and encoder 6. If the system is to be used withMRI intraoperative imaging, linear or rotary piezoelectric motors mayadvantageously be used to provide the motion.

Reference is now made to FIG. 2, which illustrates schematically how thecomplete double needle assembly 3, 4, can be advanced through the holesin the base sections, using the motor-encoder assembly 6, until thedistal tip of the assembly has accessed the region 22 of the brain whichit is desired to treat.

Reference is now made to FIG. 3, which illustrates schematically how,once the combined needle assembly 3-4 has been rotated so that thedistal opening 21 in the cannulated needle is orientated within theregion 22 of the brain to the first part to be treated, the internalflexible needle 4 can be advanced outside of the external rigid needle3, using the motor-encoder 7, so that the tip of the internal flexibleneedle can reach that part of the regions the brain which it is desiredto treat. Since in the implementation shown in FIGS. 1 to 3, the exitangle of the internal needle is fixed, the combined motion of all threemotors is necessary in order to provide access to any part of the entirevolume of the region to be treated. Thus, combined activation of themotor 6 to drive the depth of penetration of the external needle 3, andthe motor 7 to drive the extent of the lateral extension of the internalneedle 4 from the exit of the external needle, enables the fulltwo-dimensional area shown in the drawings to be accessed. The verticalarrow marked V indicates the motion direction enabled by insertion andwithdrawal of the external annular needle 3, and the angled arrow markedL indicates the direction of the longitudinal extension motion of theinner flexible needle 4, to access the off-axis region of the brainwhich it is desired to treat. In order to provide access to any part ofthe entire three-dimensional volume of the region to be treated, i.e.including cross-sections out of the plane of the drawing, it isnecessary to activate motor 5 in order to rotate the complete combinedneedle assembly by rotating base section 2, as indicated by the rotationarrows, marked R in FIG. 3. The robotic control system, using thedimensional extent of the region to be treated as determined by thepreoperative three-dimensional images generated of the region,coordinates motion of all three motors in order to gain access to anypart of the entire three-dimensional volume. Thus, a specific targetarea is reached by combination of (i) the orientation angle of thecannulated needle 3, such that its distal opening is directed towardsthe target area, (ii) the depth of entry of the cannulated needle 3, andthen (iii) the extension of the flexible needle 4, to reach the targetarea.

In FIG. 1A to 3, and the corresponding FIG. 5 later in the disclosure,the base section 2 is shown as a large baseplate covering much of theextent of the main base 1. However, it is to be understood that theso-called base section through which the internal and external needleassembly is axially mounted and rotates therewith, may be no more than acollar mounted on the external needle assembly, with a robotic mechanismfor rotating the collar relative to the main base fixed to the subject'sskull. The invention is not therefore intended to be limited by the typeof rotating base section shown in FIG. 1A, the operational feature beingthat that element be capable of controllably rotating the needleassembly around its axis.

As an alternative to accessing the lateral (longitudinal) extent of thevolume to be treated by means of the extension of the internal needle 4through a fixed angle exit port in the outer rigid cannular needle 3, itis possible to direct the angle at which the inner flexible needle isextended into the cerebral tissue, by means of an adjustable angle exitport incorporated into the external rigid cannula. One suchimplementation is shown in FIG. 4A, which is an enlarged isometricdrawing of the bottom end of the double needle assembly. According tothis implementation, the bottom end of the external cannular needle 3 isprovided with a variable angle exit aperture, through which the internalflexible needle 4 can protrude. This exit aperture can be in the form ofa pair of pins 26 attached to a rotatable pulley 28. The pins act asjaws which constrain the outer surface of the internal needle 4, anddirect it to the desired angle as the pulley 28 is rotated. The angle ofthe exit aperture can be conveniently be adjusted for instance by meansof a pair of drive wires 27 looped around the pulley 28. The outercannula 3 should be extended to cover the outer diameter of the pulleywheel and to enclose its distal end, to ensure smooth insertion of thedevice, without the pulley wheel or its pins causing unnecessary damageto the cerebral tissue. A slit can be formed in the rounded distal coverof the pulley wheel to enable the inner flexible needle to exit thecover at the desired angle,

In use, the robotic device should be inserted into the subject'scerebral tissue with the pulley positioned such that the pins are intheir lowermost position (in the sense of the directions shown in thedrawing), in line with the axis of the external cannula, and with theinner flexible needle extended far enough for its distal end to just becaptured between the pins. The pulley may then be rotated until the pinsand the tip of the internal flexible needle held within the confines ofthe pins are rotated to such an angle that the flexible needle isdirected to extend in the direction predetermined to reach the intendedtarget region. Once this angular orientation has been achieved, theinner flexible needle can be extended outwards from the outer rigidcannula, to access the region to be treated,

As an alternative to a pulley wire with pins, reference is now made toFIG. 4B which illustrates a rotatable block 30 with a channel 31 formedtherein mounted within the distal end of the outer cannular needle 3.The inner flexible needle 4 can be guided into the channel 31 while itis aligned axially with the bore of the cannulated needle, and the blockcan then be robotically oriented to the desired angle required to directthe internal flexible needle to the desired point in the subject'sbrain. The center of rotation of the guide block 30 should be near itsproximal end so that the entrance to the channel 31 remains fairlycentrally located within the cannulated needle 3, to enable smooth entryof the flexible needle 4. The robotically controlled drive motor forpulling the pulley wires to adjust the angle of this exit aperture, orto rotate the angularly variable channel block, can then be used in lieuof, or in addition to, the drive motor 6 for inserting the externalcannula, while performing the surgical procedure. By this meansadditional flexibility or additional simplicity, is available forgaining access to perform the procedure. Thus for instance, the externalcannular motor 6 can be used for advancing the operating end to the mostproximal point of the region to be treated, and the treatment itselfperformed by means of the variable angular exit aperture of the internalneedle and the exposure extent of the internal needle, as shown by theset of arrows at the tip of the internal flexible needle, together with,of course azimuthal rotation of the entire robot activation arm.According to this implementation, with the tip of the external cannularneedle at the top of the treatment region, the pulley needs to cover anangular range sufficient for covering the entire region to be treated.

The implementations of FIGS. 4A and 4B are illustrated using a pulleywheel with wires operated externally to rotate it, since such anarrangement can be readily installed within the confines of the cannularneedle 3, but it is to be understood that any other form of rotationthat does not unduly increase the outer diameter of the device canalternatively be used.

The angle though which the flexible needle can be delivered, whether useis made of the fixed angle exit port of FIGS. 1 to 3, or the variableangle exit port of FIG. 4, is dependent upon the flexibility of theinner needle and on its diameter. The more flexible the needle, thegreater the angle that can be negotiated, and the thinner the needle,the greater the angle that can be negotiated. A compromise must be madebetween the need to maintain sufficient stiffness in the flexible innerneedle to enable it to reach its planned target without being deflected,and the need for it to readily deploy from the angled outlet port at theend of the rigid outer cannula. Because of the complexity of thearrangements shown in FIGS. 4A and 4B, it is likely that they will onlybe implementable for use with fine inner needles or probes.

As mentioned in the summary section hereinabove, a number of novelconfigurations are now described for a flexible needle which can beexited through a 90° angle bend from the inner cannula, through a radiusof curvature of the same order of magnitude as the effective diameter ofthe needle itself, without suffering any irreversible buckling damage asa result of the bend. A typical requirement for the strength of such aneedle for use in cranial treatments is that a 5 gm. lateral forceapplied on a 30 mm length of the flexible needle would not result in adeflection of more than 1 mm.

It is known that when a thin-wall circular cylindrical tube, such as theflexible needle of the present system, is subjected to pure bending, itscross section becomes more oval as the radius of curvature decreases.Ovalization growth causes a progressive reduction in the shell's bendingrigidity. Eventually, a maximum value of stress is reached and furtherbending results in plastic deformation of the tube. Once this point hasbeen reached, the needle no longer behaves elastically, and cannottherefore be used in order to deploy correctly out of the outer cannula.In order to reduce the radius of curvature through which a tube can bendand even locally buckle before crossing the elastic limit, a needlehaving an initial elongated cross-sectional shape perpendicular to theplane of bending is used.

Reference is now made to FIG. 5A, which illustrates schematically thecross section of an oval shaped needle, according to a firstimplementation of a method of providing a flexible needle that willnegotiate a radius of curvature of the same order of magnitude as theeffective diameter of the needle itself, more readily than a needlehaving a circular cross-section. The axes are labeled in millimeters,showing the overall maximum diameter of approximately 3 mm. Two ovalshaped needles are shown in FIG. 5A, one 50 having an ellipsoidal shape,and the other 51, having a toroidal shape. These two shapes are bistableconditions of the tube as it bends, switching between the oval and thetoroidal cross section reversibly. However, it is to be understood thata toriodal cross section needle could also be used as the unstressedprofile before bending. Calculations have shown that in order tonegotiate a 3 mm radius of curvature without undergoing plasticdeformation, a stainless steel toroidal shaped needle having a width of3 mm should have a wall thickness considerably less than the wallthickness of standard hypodermic needles. Such a needle does havesufficient mechanical strength to be used for cranial use, and stillprovide the required 1 mm accuracy at a distance, 30 mm from the exitaperture of the outer cannula.

Reference is now made to FIG. 5B, which illustrates schematically analternative flattened profile needle, which also provides satisfactoryproperties for use in the cranial treatment devices of the presentdisclosure. The profile shown in FIG. 5B is that of an eye shape 52,showing the ovalization effect 53 taking place on bending. As the needlebends, it switches at the predetermined stress point, between the twobi-stable shapes, and returns on becoming unbent. It can be shown thatthe critical moment before plastic deformation occurs is slightly lowerthan that of the oval or toroidal shapes of FIG. 5A.

Reference is now made to FIG. 6, which illustrates schematically anotherimplementation by which a flexible needle for use in the present devicecan be constructed as a passive magnetic bead chain, made up of a stackof magnetized beads. The magnetic chain is hollow, enabling passage ofthe detection and treatment tools as required. FIG. 6 shows a sequenceof drawings as the bead chain is pushed into the outer cannula 3 by theeternally applied force F until it meets the 90 degree exit aperturecurve, as illustrated in FIG. 6. The front most bead 61 is thenpartially separated from the adjacent bead and moves forward into thecurve. The next beads 62 follows it and after exiting the curve, thebeads are reattached due to the magnetic force between them, to form theoriginal rigid beam structure. The magnetic forces acting are such as tomake the separate beads making up the chain self-centering. This passivemagnetic bead chain therefore fulfills the requirements for use in thepresent device, since on one hand, the bead chain becomes loose whilegoing through the curve, thereby enabling each bead to negotiate thecurve individually, while on the other hand, the bead chain maintainslateral strength when it protrudes from the output cannula, enabling itto sustain the external loads.

An example bead chain was constructed to verify firstly that the chainof this implementation can endure the 90 degree bend of the externalcannula; and secondly that a load bearing test verifies that the chainis strong enough upon exit from the external needle to fulfill the needsof the cranial procedures envisaged using this device. An exemplarychain of 15 hollow magnetic beads made of a neodymium rare earthmagnetic material Nd₂Fe₁₄B was evaluated. The typical magnetism of thismaterial is approximately 1,000 kA/m. Bead dimensions were: outerdiameter of 3 mm, inner diameter of 1 mm and height of 2 mm, resultingin a magnetic moment of m≈50 Am². Two channels were examined, withinternal diameters of ˜3 mm and 3.3 mm, and in both cases, the beadssuccessfully negotiate the curve, though in a slightly different manner.

In order to perform his strength test of the magnetic bead chain, themagnetic bead chain was horizontally fixed at one edge and weights werehung on the other edge, at two locations. The chain failed at weights of12 gr and 8 gr, 2 cm and 2.6 cm from the first bead, respectively. Theresults of this feasibility trial show that the chain tested issufficiently rigid to use as a solution for the internal needle, beingstrong enough and expected to retain the required accuracy level.

Reference is now made to FIG. 7 which illustrates a furtherimplementation of the flexible needles for use in the system of thepresent disclosure, in the form of an inflatable annular shaped balloon71, negotiating the curve at the exit of the outer cannula 3. Theballoon should be constructed of a material sufficiently strong and yetsufficiently flexible to provide the properties required of theinflatable needle. Kevlar is a good candidate for such an inflatableneedle balloon. At a sufficiently high filling pressure, the annularballoon has sufficient strength to fulfill the requirements of thisapplication with regard to reaching the target accurately without beingdeflected by the small lateral forces that may arise during its passagethrough the brain tissue, yet the high lateral forces exerted on by theexit curve of the outer cannula enable it to bend sufficiently tonegotiate the bend. The center of the annular balloon 72 can then beused for passage of a surgical or therapeutic tool or probe.

Reference is now made to FIG. 8, which illustrates yet another “flexibleneedle” construction, utilizing a tensegrity structure to provide thestructural strength combined with the required flexibility whennegotiating the bend at the exit of the outer cannula. A tensegritystructure is based on the use of rigid components 81 in compressioninside a net of continuous pretensioned cords or wires 82. Deployabletensegrity structures have been widely investigated for use in aerospaceapplications. Such structures are light weight, yet strong enough due totheir special structure. A miniature passive tensegrity mast withsimilar bi-stable struts using elastic fabric instead of cables as thepretensioned elements for manufacturing simplicity can be used as the“flexible needle” element of the present application.

The tensegrity mast is constructed so that it has good compressive andtensile strength, and a predetermined lateral strength also. Thetensegrity structure is subject to two different levels of lateralforces. As the structure progresses through the brain tissue, althoughthe tissue itself presents only a low level of longitudinal resistanceto that motion, there may be lateral forces exerted on the mast becauseof other elements present in the brain, such as blood vessels, which aresubstantially firmer than the brain tissue itself. Such lack ofmechanical isotropy in the tissue may exert lateral forces on thetensegrity structure as it proceeds, and because of the need foraccuracy, the structure must be sufficiently strong to withstand suchlateral forces with a minimal predetermined deflection. On the otherhand, during entry through the bend in the outer cannula, when theleading edge corner strut of the tensegrity mast first impinges on theouter curved wall of the inside of the exit bend of the outer cannula,it undergoes lateral forces of such a level that the structure collapseslocally by release of the tension on the connecting wires to that strut,and the mast can begin to negotiate the bend. The structural integrityof the remainder of the structure is unaffected, such that thelongitudinal force driving the structure through the curve in theexternal cannula does not cause collapse elsewhere. As each elementpasses the beginning of the curvature, it too gives under the lateralforces, retensioning itself as the curve is completed. These lateralforces are substantially higher than the lateral forces exerted bymechanical anisotropy in the brain tissue. The tensegrity structure isconstructed with struts and tensioned wires calculated such that itsresistance to collapse when lateral forces are applied to it is suchthat it readily negotiates the curvature of the outer cannula, but hassufficient resistance to maintain its integrity when lateral forcesexpected from passage through the brain tissue are experienced. Methodsof designing and constructing such tensegrity structures are well knownin the art, such as in the reference volume by R. E. Skelton et al,entitled “An Introduction to the Mechanics of Tensegrity Structures,” inThe Mechanical Systems Design Handbook: Modeling, Measurement, andControl, published by CRC Press; III (17) 2001. It is to be understoodthat in the implementations shown in FIGS. 6 and 8, i.e. the magneticbead chain and the tensegrity structure, and to a lesser extent, alsothe annular balloon implementation shown in FIG. 7, the nature of the“flexible needle” is such that it does not itself generally act as thesurgical tool element or as the drug delivery conduit, but rather actsas a guide channel reaching the application target region, and that theoperative surgical or therapeutic element may be threaded down the“flexible needle” to the target region. However, in some applications,such structures do indeed behave as part of the operative elementitself, such as being part of a probe or an electrode, such that theterm “flexible needle” is to be understood to be cover all suchimplementations and uses. It is to be understood that the specificembodiments shown in FIGS. 1 to 8 are only possible examples of how toimplement the robotic neurosurgical systems described in the presentapplication, and that they are not intended to limit the scope of theinvention of the present application, which is based on the use of apair of concentric needle elements for accessing the region to betreated, even if in the depth of the brain, by means of a small incisionand a narrow access path. The outer one is a rigid guide element and theinner one is a flexible operating element—flexible such that it can bedirected out of the inner guide at a desired angle, and an operatingelement because it is equipped with the desired tool for performing thesurgical or diagnostic procedure to be undertaken. Access to any part ofthe region to be treated is provided by combinations of motion of theinner and outer elements.

Use of the device according to any of the above describedimplementations, thereby enables the execution of comparatively largevolume procedures within the interior of the brain, yet without causingmore trauma to the rest of the brain than that of the insertion of theexternal cannula along its narrow path. Thus, use of the roboticneurosurgical device of the present application, using minimal accessfrom a small burr hole in the skull, enables the treatment of asubstantially large volume of the brain with minimal collateral traumato those parts of the brain not being treated. Furthermore, because ofthe simplicity of the access method used, the surgeon can choose theaccess path such that it causes least trauma to the other parts of thebrain, even though that path may be longer than the closest path fromthe skull to the region to be treated.

As previously mentioned, treatment of the desired region can beaccomplished either by means of a cutting instrument at the distal endof the internal needle, or by means of an electric current, or byablation by means of energy delivered down the internal needle, or bymeans of drug delivery to any or all parts of the region to be treated.Delivery of heat or light can be very advantageously performed usingfiber optical delivery, with the optical fiber either replacing theinternal needle completely, or being threaded through the internalneedle, with its termination at the tip of the internal needle.Additionally, biopsies of any part of the region be treated can besimply executed using biopsy pincers at the end of the internal needle.

Reference is now made to FIG. 9, which illustrates schematically acomplete practical robotic system based on the above describedimplementations, including a number of safety features required by sucha system for performing neurosurgery. In the first place, in order todefine the position of the robotic system activation arm relative to theposition of the region to be treated, as determined from preoperativethree-dimensional images, some registration features must be provided.In the presently shown implementation, this is achieved by the provisionof preferably three or more pins 17, 18, inserted into the skullpreoperatively, such that their position is uniquely defined in thepreoperative three-dimensional images. These pins are inserted atpositions which are predefined to match the mounting holes in the mainbase 1 of the robotic system, such that when the system is mounted onthese pins, its position is registered relative to the data of thepreoperative three-dimensional images. The robotic control commands tothe distal end of the internal needle of the activated arm can thus berelated to the position of features shown in the preoperativethree-dimensional images.

In addition in FIG. 9 there are shown back-up sensors and encoders forevery motion function of the robotic system, as required by the safetyregulations for use of such systems. Thus for instance the physicalposition of the internal flexible needle may be determined by primary 10and secondary 11 encoders, while the electronically determined positionof the motor driving the internal flexible needle may be determined byprimary 8 and secondary 9 encoders. Additionally, the physical positionof the external rigid cannular needle may be determined by primary 13and secondary 14 encoders, while the electronically determined positionof the motor driving the external rigid cannular needle may bedetermined by primary 15 and secondary 16 encoders. Furthermore anencoder 12 for the rotating platform angular position is also provided.This encoder also generally has a back-up (not shown in FIG. 9). Theencoders descried in this disclosure may include optical, magnetic,electrical, or inductive encoders. All of the sensors, motors andencoders are connected to the robotic controller, which, for simplicity,is not shown in FIG. 9.

Additional sensors can be incorporated at the distal end of the flexibleneedle, to provide additional information or additional guidance to thesurgeon. Thus, in FIG. 9, there is shown a representation of anelectrophysiological or optical sensor 19, for tissue diagnosis. Inaddition, an ultrasound sensor can be added, such that it detects theneedle location in real time as well as the boundaries of the diseasedarea. The ultrasound sensor can be located either on the flexible needle19, or on the external rigid cannula 23. In the latter case theultrasound sensor can sense both the flexible needle tip as well as thetumor boundaries. It is sufficient to detect only the diseased areaboundaries, as the relative position between the flexible needle tip andthe rigid needle mounted ultrasound sensor is known from the robotcontrol system. An infra red sensor that can detect and distinguishtissue properties some distance inside a tissue can alternatively beused for this purpose. Such optical sensors can detect, for instance,fluorescence effects in tissues, to label specific types of cell towhich the appropriate fluorescing drug attaches. Similarly, an electricsensor that can detect the differences in electric properties betweenhealthy and diseased tissue can be added to the needle tip.

Furthermore, the camera of an imaging system 25 is shown in FIG. 9, suchthat intraoperative images of at least some of the region 22 of thebrain being treated, the needle tips, the main base 1 and its skulllocating elements 17, 18, can be obtained, most advantageously togetherwith anatomic features of the subject's skull and/or face. Such imagescan be used for monitoring the position of the needle tips, and forproviding information for performing a registration of the roboticdevice with the preoperative images available.

Finally, reference is now made to FIG. 10, which illustratesschematically further exemplary implementations of the needle insertiondevices described in this disclosure. In FIG. 6 there is firstly shownan alternative method of fixing the robotic device of the presentapplication to the skull 60 of the patient being treated. This isillustrated in FIG. 6 using a phantom skull only in order to show thefixation method. Instead of being attached by means of a base unit whichis screwed directly into the skull of the patient, as is shown in theprevious implementations, in FIG. 10, the needle insertion system issupported on a stereotactic frame 61, of any type that is known in theart, though an y other type of frame defining the position of therobotic device relative to the skull may also be used. As an alternativeto a stereotactic frame, a Mayfield clamp may alternatively be used,though in this case, there will be need to perform a registrationprocedure in order to define the position of the clamp and the deviceattached thereto to the preoperative images, such as by surface featurematching or fiducial markers. In the implementation shown in FIG. 10 theangular alignment scale 62 is shown for only one azimuthal orientation,but it is to be understood that the other two azimuthal orientationsalso have scales to enable alignment to be made in those angulardirections too. The device is attached by means of a rotatable base unit63, and the needle assembly, 3, 4, with its robotic controls 6, 7 areinserted through this rotatable base assembly in a similar manner as inthe previous embodiments of FIGS. 1A to 9.

FIG. 10 also illustrates an alternative use of the device of the presentdisclosure, to improve prior art methods of determining the direction ofpenetration of a treatment needle used in neurosurgery. In such a priorart methods, the region to be treated is defined on preoperative images,which include the mounting hardware used to support the needle insertiondevice. This mounting hardware could be the relevant parts of astereotactic frame or of a Mayfield clamp. The surgeon then defines theorientation angles and depth of penetration of the needle, using thealignment facilities provided on the mounting hardware. Since the samemounting hardware is registered in the preoperative images, the surgeoncan then access the intended target using calculated angles and depthsfor that mounting hardware. Using prior art methods of a single needleinserted straight into the patient's brain, there may be situationswhere access to the target point is problematic because of sensitive ordamage prone regions of the brain in the direct linear access path.

According to an alternative use of the system of FIG. 10, where astereotactic frame implementation is illustrated, the same registrationprocedure can be used as described above, but instead of aligning theprior art linear entry needle directly at the target, the surgeon canuse the present device to circumvent any regions on the linear pathwhere access is contraindicated. In use, the surgeon may plan an“articulated” safe entry path, using the pre-operative images. Thesurgeon then aligns the needle assembly 3, 4, in the correct angulardirections, using the head clamp scales 62, and the graduated base scale63 of the device, and then actuates the entry procedure described abovein connection with the embodiments of FIGS. 1A to 9, firstly insertingthe external cannular needle 3, using the drive motor 6, and then,deploying the flexible needle 4, using the drive motor 7. As analternative, a variable opening cannular needle can be used as describedin FIGS. 4A and 4B. The device is thus able to access in two dimensions,locations which would otherwise be problematic to reach by a directlinear path. The specific target area is reached by controlledcombination of (i) the depth of entry of the cannulated needle 3, andthen (ii) the extension of the flexible needle 4, to reach the targetarea.

It is appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly shown anddescribed hereinabove. Rather the scope of the present inventionincludes both combinations and subcombinations of various featuresdescribed hereinabove as well as variations and modifications theretowhich would occur to a person of skill in the art upon reading the abovedescription and which are not in the prior art.

We claim:
 1. A robotic device for performing an intracranial procedureat a target region of a subject's brain, comprising: a baseplate adaptedfor mounting on a skull of a subject; a rotatable element disposed onsaid baseplate, and having an opening in its central region; a cannulahaving an axis mounted on said rotatable element coaxially with saidopening, and which rotates with rotation of said rotatable element, saidcannula being robotically controlled to provide motion into and out ofthe skull of said subject, and having in its distal region, a curvedsection leading to a non-axial aperture disposed essentially at rightangles to said cannula axis; and a chain of magnetized beads disposed insaid cannula, said chain of magnetized beads being controlled to providemotion around said curved section and out of said non-axial aperture,and having a structure in which each magnetized bead is adapted topartially separate from its neighboring magnetized beads whennegotiating said curved section, and to reattach itself to itsneighboring magnetized beads after exiting said non-axial aperture, themagnetization of said chain of magnetized beads being sufficiently highto enable said chain of magnetized beads to continue said motion out ofsaid non-axial aperture to said target region without losing itsmechanical properties; wherein coordinated control of the motion of saidcannula and said chain of magnetized beads and rotation of saidrotatable element enables access to be obtained by said chain ofmagnetized beads to said target region of the brain; and wherein anoutside diameter of said chain of magnetized beads is no larger than 4mm, and a radius of curvature of said curved section is no more than 25%larger than an external diameter of said cannula.
 2. The robotic deviceaccording to claim 1, wherein said chain of magnetized beads aremagnetized in a direction such that they are attracted to each other toform a self-centering stack.
 3. The robotic device according to claim 1,wherein said chain of magnetized beads comprises a cutting tool, suchthat resection of a brain tumor can be performed such that anycollateral trauma to those parts of the brain not being treated isapproximately confined to a region having a width of said cannula. 4.The robotic device according to claim 1, wherein said chain ofmagnetized beads is adapted to be connected to an energy deliverysystem, such that ablation or optical or electro-treatment of a braintumor can be performed such that collateral trauma to those parts of thebrain not being treated is approximately confined to a region having awidth of a first cannulated needle.
 5. The robotic device according toclaim 4, wherein said chain of magnetized beads comprises an opticalfiber for delivery of energy via said energy delivery system.
 6. Therobotic device according to claim 1, wherein said chain of magnetizedbeads comprises a biopsy tool, such that biopsy samples may be obtainedfrom regions of the brain at different positions laterally displacedfrom each other by distances substantially larger than a width of afirst cannulated needle, such that collateral trauma to those parts ofthe brain not being accessed is approximately confined to a regionhaving the width of said first cannulated needle.
 7. The robotic deviceaccording to claim 1, wherein said chain of magnetized beads comprises adrug delivery passage.
 8. The robotic device according to claim 1,wherein said chain of magnetized beads comprises a sensing deviceadapted to differentiate between healthy and non-healthy tissue.
 9. Therobotic device according to claim 1, further comprising a set ofpreoperatively inserted markers for relating a position of said roboticdevice to the skull of the subject, such that a co-ordinate system ofsaid robotic device can be registered to a preoperative image of theskull of said subject.
 10. The robotic device according to claim 1,further comprising at least one position sensor disposed either in adistal region of said chain of magnetized beads, such that a real timeposition of a tip of said chain of magnetized beads can be monitoredintraoperatively, or in the distal region of said cannula, such that thereal time position of the tip of said cannula can be monitoredintraoperatively.
 11. The robotic device according to claim 1, whereinsaid structure of said chain of magnetized beads is such that itsflexibility is reduced on negotiating said curved section, and itsmechanical properties are regained after deployment from said non-axialaperture.